Hi,

Do you mean all pages/posts on your site or only "Pages" in "Dashboard > Pages"?

If you mean about all pages/posts on your site, please check options for it via:

a) Customize > General Options > un-check on "Enable Sidebar on Homepage" & "Enable Sidebar on Archive"

b) Customize > Single Post Options > Single Posts Sidebar Layout > select "No Sidebar" or "No Sidebar with Container Width Smaller"

c) Customize > Page Options > Page Default Template Layout > select "No Sidebar with Container" or "No Sidebar with Smaller Container Width"

If you mean about all "Pages" in "Dashboard > Pages", just need check option for it on point c) above.

Best Regards,

PenciDesign